High voltage cable splice using condensation reaction polymeric insulation

ABSTRACT

A method and composition for effecting splices of high voltage cable sections for use with a mold placed around the cable sections. The composition comprises a liquid polyolefin, a finely divided solid polyolefin and a chain extension agent capable of reacting with condensation reaction moieties of the liquid polyolefin.

This is a divisional of application Ser. No. 874,105, filed Feb. 1,1978.

FIELD OF THE INVENTION

This invention relates to the field of electrical cable splicing andmore particularly to a novel technique for providing insulated splicesfor high voltage cables.

BACKGROUND OF THE INVENTION

High voltage cables that are used to transmit substantial quantities ofelectrical power either above ground or underground, frequently requiresplicing either during the installation in the field, or during downtime, ie. repair. Several general techniques are known for handling suchsituations.

One method known to applicant is to provide a traditional cable splice,and to then take the spliced section of cable, insert it into aprotective sheath or housing, and encapsulate the spliced cable segment.Such a technique and the apparatus therefore is disclosed and claimed inthe Hankins et al U.S. Pat. No. 3,992,569 assigned to HexcelCorporation.

Another technique is disclosed in Filreis et al U.S. Pat. No. 3,879,249wherein a stiff resilient polymeric plastic sheet having a specialsurface of grooves and lattice work is provided and which sheet may beshaped to form a closure or mold about a splice. As a closure, dirt anddust are sealed out, and as a mold it can serve to shape insulatingself-curing resinous compositions applied in a liquid form about thesplice.

A very common technique employs a liquid potting method, which isreasonably economical but is primarily intended for low kilovolttransmissions because the materials available for the potting do notbond well to the cross-linked polyethylene or ethylene-propyleneinsulation used on high voltage cable. Applicant is aware however of aliquid slurry method claimed by Nakata in U.S. Pat. No. 3,996,081 issuedDec. 7,1976 to be suitable for high voltage cable splice application.

One of the more popular techniques involves the use of tape wrappingfollowed by the application of high pressure by means of a hydraulicpress and subsequent cure at elevated temperatures. This technique isnot only costly, but slow, due to extended cure cycles The emphasistoday is on the development of in the field splicing techniques whichhopefully can be provided quickly and cheaply while being suitable forhigh voltage applications. A paper covering Hexcel Corporation'sresearch and development of a field molded splice for use on eithercrosslinked polyethylene or ethylene propylene rubber insulated, soliddielectric cables was presented at the IEEE Southeast Conference in1975. This paper relating to that company's HOTSPLICER.sup.™ isincoporated herein by reference. A patent known by applicant thatrelates to such a tape wrapping technique, but not assigned to Hexcel isU.S. Pat. No. 3,970,488 issued July 20, 1976 to Nelson. As is recitedtherein, the generalized technique for making such a tapewrapped splicerequires that the ends of the two cables to be spliced together aresubjected to a plurality of steps. Firstly, they are prepared byremoving a portion of the outer cable jacket, folding back theelectrically conductive outer metallic shield, removing a portion of theunderlying outer semiconducting screen, penciling the cable insulationdown to the inner semiconducting screen, and removing a portion of theinner semiconducting screen to expose the central conductors. The twoexposed central conductor end portions are next mechanically andelectrically coupled together by means of a conventional connector, e.g.a connector sold in the trade as a CADWELD connector. The splice is nextcovered with one or more layers of semiconducting tape, and anelectrically insulative jacket is molded onto the splice and adjacentregions of the cable insulation, after which a layer of semiconductingmaterial is applied to the outer surface of the insulative mold, a layerof metal gauze material is wrapped around the semiconductive material,secured in place and soldered to the electrically conductive outermetallic shield and the splice is finished off with a layer ofconventional electrician's tape.

The insulative jacket is molded to the cable splice by wrapping stripsof semiconductive molding compound over the semiconducting tape,wrapping strips of electrically insulative thermosetting moldingcompound under heat and pressure into the mold chamber to soften thesemiconducting and insulative molding compounds and bond them to thevarious surfaces with which they make contact, and curing the moldedsplice.

SUMMARY OF THE INVENTION

The concept of this invention is to provide a monolithic structure ofcross linked insulation for the splice of two high voltage cables.

The cable is stripped, the semiconducting strand screen is exposed bycutting back the insulation, the insulation is shaped at its termini.The cable ends are joined by crimping the two together or by weldingwith fusible alloy. Semiconducting tape is wrapped in place. A mold isfixed in place, and a castable composition of this invention is addedand allowed to cure to a monolithic impermeable structure which isbonded to the insulation material of the cable, and also to thesemiconducting strand screen and the optional semiconducting insulationscreen if present.

Accordingly it is an object of this invention to overcome thedisadvantages of the prior art splicing systems.

Another object is to provide an easy to use field employable cablerepair system.

Yet another object is to provide a cross linked plastic outer layer fora high voltage splice that bonds to both the insulation and thesemiconducting strand screen.

A further object is to provide a two step cure which includes a chainextension followed by a graft copolymerization.

Yet another further object is to employ as the chain extended liguidpolyolefin for reaction with cable insulation, one or more liquidpolyolefins having at least one condensable moiety thereupon which ischain extended by a condensation reaction.

For a fuller understanding of the nature of advantages of thisinvention, reference should be made to the following detaileddescriptive taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view showing the cable splice of thisinvention in the mold.

FIG. 2 is a side electrical view showing one embodiment of insulationlayer end shaping according to the invention.

FIG. 3 is a side sectional view showing a second embodiment ofinsulation layer end shaping according to the invention.

FIG. 4 is a perspective cutaway view showing a mold as in FIG. 1 withtwo electrically joined cable sections therein.

DESCRIPTION OF PREFERRED EMBODIMENT

As can be seen from FIG. 1, two cable sections are to be joinedtogether, one of which is shown in both FIGS. 2 and 3. The differencebetween the two figures refers solely to tailoring and not to thedetails of the cable unit per se.

It is understood that the two cables of FIG. 1 are substantiallyidentical and as such only one will be described in detail.

Each cable section comprises a conductor section 14, insulation 16surrounding the conductor section, a a tubular metal sheath 18surrounding the insulation 16. Sheath 18 can be either of sheet, tapedor braided construction. Each cable section, as seen in FIG. 2, has beenprepared for formation of the splice by removal of insulation 16 fromits end to provide an exposed end portion of the conductor section andby removal of some of the metal sheath 18 to provide exposed insulation16 projecting past the end of the metal sheath. The end of insulation 16is preferably formed into a tapered configuration, as illustrated inFIG. 2.

The only differences between FIG. 2's embodiment and that of FIG. 3 isin the end treatment. That end strand of FIG. 2 is designated by apencil taper end shape while that of FIG. 3 is a notch configuration ofthe insulation. Either of these or any other suitable configuration forend treatment of the insulation layer 16 may be employed with theinstant insulation.

In order to practice my invention, the following general procedure isemployed: The cables 12 and 14 to be joined are stripped clean at theends for a sufficient length to allow for adequate handling. Then thecable insulation 16 is cut back from each end to provide adequateexposure of the semiconducting strand screen, 20. The insulation layeris end shaped using standard cutting tools preferably to a pencil taper,per FIG. 2 or a notched configuration, FIG. 3; or to any otherconvenient configuration. The metal cable ends, 14, are then joined byusing a conventional crimping device or by welding with a fusible alloy,such as the commercially available Cadweld® joining compound. The joint24 is made smooth, and a uniform layer of semiconducting tape 22 isapplied. The operator is urged to make sure that it, 22, overlaps thesemiconducting strand screen 20 at both ends of the joint. Next, twohalves of a metal mold, 80 as seen in FIG. 4, are applied and fixed inplace as is known to the art. The mold preferably lined withsemiconducting layer 90, is placed in preferably horizontal position andone of the castable compositions 84 of my invention is added. Heat isthen applied sufficiently to cure the specific casting composition used.Upon cure, a monolithic, water impermeable structure results within themetal mold, which is bonded to the cross linked polyethylene (or crosslinked polyethylene-propylene) cable insulation and to thesemiconducting strand screen 20, and to the semiconducting insulationscreen 18, if this latter is present.

As indicated above, after the cable ends, (conductors,14L and 14 R) havebeen joined and a covering of semi-conductor material such as tape 22 isapplied, the junction is placed into a mold 80.

Mold 80 may be constructed of aluminum, copper, steel, or any of theconducting alloys available in the marketplace. Preferably mold 80 islined with a semi-conducting coating 90, to protect against coronadischarge. Mold 80 is placed preferably in a horizontal position, forease of filling, and tightened in place by adjusting hose clamps 94, bytightening screws 96, on the flanges 92 of mold 80. Obviously somesuitable means may be employed to prevent leakage, such as a gasket notshown, interposed between 18 and 92 if such is found necessary. Alsoother closure means adapted to hold the two halves of mold 80 togethermay also be employed.

Mold 80 is seen to have at least one entry port 82, here 2 are employedto allow for air escape during the addition to the chamber of the mold100 of the casting compositions of this invention. These ports, 82,communicate with the chamber and have a threaded opening, 88, which isclosed off by a removable threaded-in-place cap, not shown.

In order to prevent a dielectric breakdown from being initiated withinthe region of the junction occupied by the casting composition, 84, itis important that the resin 84 be added and maintained in such a manneras to prevent the formation of voids.

The compositions of this invention are added to chamber 100 throughports 82 in an amount sufficient to fill the chamber 100 up to the layer90. Mix 84 is poured, pumped or injected in any manner that is known tothe art. Heat is applied to the exterior of the mold 80 to betransferred to the curing resin 84. Heat may be applied by the use ofstrip heaters, heating jackets or the like, all of which are known tothe art. The amount of heat to be applied is contingent upon the mixbeing added, and the particular size of the mold but is readilydiscernible to the skilled artisan.

The likelihood of the formation of voids in the curing resin can besubstantially reduced by deaerating the resin prior to its addition tothe chamber.

Upon cure, which will usually take place in longer durations of time, ifthe aforesaid heat is not applied, a monolithic water impermeablestructure results within in the mold. Upon release of the mold portions,as by unscrewing screw 96 and removing clamps 94, it is found that thecured resin is bonded to the cable insulation 16, and to thesemi-conducting strand screen

If, depending upon the manufacturer of the cable, an insulation screenis part of the cable as the outer most layer, it should be soldered tothe metallic mold.

For the reader's information, it has been found that the insulationlayer of high voltae cable is generally either cross-linkedpolyethylene, or cross-linked polyethylene-propylene.

In the embodiment depicted in FIGS. 1 and 4 of a mold suitable for useherein, funnels 103 have been added and are shown threadingly engaged tothe threads 86 of opening 88. These funnels 103 render addition of thecast mix 84 easier. Upon completion of the cast mix addition, funnels103 are removed and a threaded cap not shown is secured to 82. By use ofsuch a cap no mix can escape to cause voids in the monolithic structureto be formed.

In FIG. 4 an electrically joined, tape wrapped splice is shown insertedin the mold 80. This mold does not have the lining of semi-conductivemastic as is seen in FIG. 1.

The description of the mold employable herein should not be read in alimiting manner. Thus any mold with entry means for addition of the castmix, and having suitable closures to maintain the cable ends fixedly inplace during during of the chemical composition may be employed.

GENERAL CHEMISTRY

In the practice of the instant invention it is seen that a liquidpolyolefin which may or may not have pendent funtionality is firstchain-extended. In those instances where there is pendent functionalitysuch as hydroxyl, carboxyl and the like, chain extension can take placeby the addition of another liquid polyolefin which has different pendentgroups capable of entering into a condensation reaction with any of theknown condensable pendent groups either aforesaid or not mentioned.Alternatively, instead of employing a second liquid polyolefine for"internal" chain extension, another ingredient can be added herein isdesignated as an external chain extender, and which would also bearcondensable moieties thereupon. For example, such compounds wouldinclude polyols to react with liquid polyolefins having condensablefunctionality. The concept of chain extension by condensation is wellknown and further details need not be cited presently.

If the liquid polyolefin does not have condensable pendentfunctionality, chain extension may take place by free radical catalysisto break the double bond and to add thereupon. Typical of such areaction would be the addition of an organo mercaptan to such apolyolefin. Details of the use of non-functional liquid polyolefins forthe preparation of casting compositions for reaction with cross-linkedcable insulation part of the subject matter of my co-pending applicationSer. No. 874,104 filed concurrently herewith.

It is also to be seen that the practioner may choose to chain extend aliquid polyolefin which does have condensable pendent moietiesthereupon, by a free radical initiated reaction. The use of such liquidpolyolefins for the preparations of casting compositions for reactionwith cross-linked cable insulation is also disclosed and claimed in myaforesaid co-pending application. The liquid olefin (LPO) is used withsolid polyethylene (PE), see infra. It is seen that the chain extendedliquid polyolefin and PE is placed in a mold, heated to gelation andthen allowed to react with the cross-linked cable insulation which isusually cross-linked polyethylene or cross-linked polypropylene-ethyleneas well as the solid PE powder to form a single monolithic cross-linkedstructure.

In the instant invention the liquid polyolefins to employ are those ofthe general formula: ##STR1## whrein Vi is a vinyl side chain; B is thebackbone of the polymer and contains at least one unsaturated doublebond; G represents non-reactive side group substituents selected fromthe group consisting of cycolalkyl, alkyl, aryl, aralkyl, iodo, bromo,chloro, cyano, carbalkoxy, and alkoxy. Fn is a functionalchain-extendable moiety each of which may be the same or different.Wherein m is a number of at least one, x is a number from 0 to about 5;Fn is a moiety selected from the group consisting of: --OH, --COOH,--NH₂, --SH, --C═CH, --NCO, ##STR2## And q designates a molecular weightrange of 300 to 10,000. Preferably x will vary from 2.1 to 2.5 and qwill preferably range from 500 to 6,000.

According to the instant invention, it is possible to employ unsaturatedliquid polyolefins with hydroxyl, carboxyl, amino, thiol, epoxy andisocyanato functional groups. The commercially skilled chemist willrecognize that only hydroxyl, carboxyl and amino functional liquidpolyolefins are readily available in the marketplace. However, theskilled artisan, can prepare those other raw materials for use in thisinvention using the commercial compounds available.

Typical reactions that may be employed to prepare thiol, isocyanato andepoxy terminated products are as follows:

1. Thiol terminated liquid polyelefin

    R-CO.sub.2 H+Acetyl Chloride (High Boiling Point Solvent)→R-COCl R-COCl+NH.sub.2 CH.sub.2 CH.sub.2 SH→R-CO-NHCH.sub.2 CH.sub.2 SH

2. Isocyanato terminated product

    R-NH.sub.2 +Phosgene (High Boiling Point Solvent)→R-NCO+HCl

3. Production of Epoxy termination ##STR3##

In all of the above R is an unsaturated liquid polyolefin moiety.

As has been indicated above, the LPO which has been chain extended ismixed with a solid polyolefin (PE) which is preferably finely dividedand used as the casting composition with the cable insulation. Thepurpose of employing the solid olefin is to produce a graftpolymerization of the residual unsaturation within the chain extendedLPO with the (PE) in addition to the reaction of the LPO with activehydrogen atoms of the cable insulation by free radical polymerizationinitiated by the peroxide present. These two reactions take placesimultaneously to form a strongly bonded single composite structureincluding the cable insulation.

While the term (PE) has been used, the solid finely divided polyolefincan be not only polyethylene, but also polypropylene,polyethylene-propylene, polybutene, polypentene, polyhexenepolycyclohexene, polystryene, polyvinyl toluene, polyethylene-vinylacetate copolymer, polystryene-butadiene and polyvinyl chloride amongothers. Only those polymers, crystalline or not, which are not readilyswollen by the balance of the liquid castable system of this inventionat ambient temperature can be employed.

It is advantageous to have a mixture of various particle sizes of thefinely divided high molecular weight solid polyolefin, to achievemaximum packing density of the fine particles and still yield goodcastability. Thus I prefer a bimodal or trimodal size distribution.Needless to say, the solid polyolefin can consist of a plurality of themembers of those within the class provided that each member meets thecriteria set forth above. I have found that the addition of 25 to 60percent of the weight of the total system of the (PE) is satisfactory,and that 40 to 50% by weight addition provides good flowcharacteristics.

THE CHEMISTRY TECHNIQUE

The casting compositions for reaction with the cable insulationaccording to the this invention are prepared by premixing theingredients under vacuum to eliminate entrapped gas and air bubbles.There are a variety of standard differential speed, batch and continuoustype mixers which may be employed. The blades may be horizontally orvertically oriented. The mixer is loaded with the liquid polyolefin,optionally a second liquid polyolefin if chain extension is to becarried out internally, as defined herein, and/or one or more chainextending agents, an optional viscosity reducing agent, such as a liquiddiolefin, as is discussed herein, and of course the finely divided solidpolyolefin. This solid polyolefin may be bimodal, as is discussed indetail herein, as well as trimodal which is also contemplated herein.Mixing is carried out under vacuum for all of the ingredients.

If immediate useage is to transpire on site, then any catalysts requiredshould also be included in the mixture, such that chain extension togelation can commence. The mix is then placed into the mold with thepre-prepared insulation section, heat applied, and reaction with theinsulation allowed to take place.

If however, field use is contemplated, and the activated reaction mix isnot shelf storable then the catalysts should not be added to the mixer,but packaged separately, and the main reaction mix should be packagedfor shipment to the field location. For such field useage, I prefer tounload the mixer by loading the casting mix into plastic bags ofpredetermined size according to the intended size of the electricalsplice. These bags after filling are to be evacuated to remove aypossible entrapped air and then sealed. The plastic bags preferably havea divided section or partition or plastic capsule, which will containcatalyst or catalysts, dissolved or dispersed in a non-volatile liquid,which preferably has therein dissolved a dye of distinctive color. (Thisnon-volatile liquid may be any of the subsequently mentioned monomericliquid diolefines such as diallyl phthalate, etc.). When it becomesnecessary to prepare the liquid casting system for use, the plasticcontainer and contents are warmed by some convenient means to atemperature which provides adequate fluidity, the partition removed orbroken and the catalyst mixture kneaded into the casting slurry until auniform mix as determined by color is achieved. Then the bag isconveniently cut or punctured at one end and the casting slurry pouredor squeezed into the ports or funnel of the metal mold prepared for thesplice. Squeezing out the contents of the plastic bag may beconveniently carried out by hand or the bag may be inserted into areservoir of a hydraulic or screw actuated injector. While the mold isbeing filled, I have found that it may be convenient to aid in theremoval of entrapped air bubbles by mechanical vibration. This can bedone by attaching any of the commercial types of air or electricallydriven mechanical vibrators to the body of the mold. The casting mix ispoured into the mold until it is completely full and rises up into thestem of the ports or funnel. Heat is then slowly applied until the firstcure temperature is reached. In general this will be in the range of50°-110° C. although I usually prefer a range of 70°-100° C. However itmay also be higher or lower than these temperatures. For either site orfield use, heating is maintained at this initial cure temperature untilgelation has been achieved. Generally this may require about 20 to 50minutes and then the temperature is elevated up to the final curetemperature. I have found that a convenient and practical range for cureis between 135°-180° C. At these temperatures the reaction mixture caneffectively soften and penetrate into the surface of the cross-linkedcable insulation and form a homogeneous bond by graft polymerizationwith that surface, as well as with the suspended solid polyolefineparticles. In general I have found that good cures can be achieved whenthe total mass of the splice has been held at the desired curetemperature for about 30 to 120 minutes. As would be expected, the rateof cure is a function of temperature and the catalyst used. Althoughmore rapid cures may be attained at the higher temperatures, there isless strain imposed upon the total system after cooling, if the curetemperature is maintained in the lower range.

It is to be understood that while I have suggested the use of a mono ormulti compartment plastic bags or plastic cartons that are inert and notreactable with the mixture, the use of same is not required and is notcritical to this invention. The advantage of same however, is thatpackages or billets may be pre-prepared for field use at a masterfacility.

In practicing my invention I prefer to use any of a variety ofcommercially available liquid polyolefines. Many such materials are theso-called liquid polybutadienes, although they may also be copolymers ofbutadiene-acrylonitrile or butadiene-styrene, and they may also containminor amounts of other momomers, which provide specific types offunctional end groups.

Typical examples of commercially available liquid polyolefines are thoseproduced by B. F. Goodrich Chemical Company under the trade name HycarCTB, CTBN, CTBNX and ATEN: Phillips Petroleum Company's Butarez CTBB,HTPB and NF series; United Technology's CBAN and ABAN liquid elastomers;ARCO Chemical Company's R-45M and R-45HT series; and there are manyothers. It is also within the scope of this invention to use liquidpolyolefins, based on isoprene, cyclohexadiene, cyclopentadiene,cyanoprene, conjugated vinyl cyclohexene and chloroprene.

Any of the diolefines may be copolymerized with each other as well asbutadiene and with or without acrylonitrile, styrene and other monomers,which may provide functional groups. Generally these liquid polyolefinesare relatively low in molecular weight, ranging preferably from 2000 to5000, but they may also be lower or higher than these values i.e. 1500to 6000.

Since it is preferable to use materials of low viscosity to obtain themost desirable flow characteristics, I have found it advantageous todilute some of the higher viscosity liquid polyolefines with lowvolatility, liquid, monomeric non-conjugated diolefines. As preferreddivalent monomers the diallyl phthalates, allyl diglycol carbonate (PPGChemical's CR-39), hydroquinone diallyl ether, resorcinol diallyl ether,1,9-decadiene, divinyl cyclohexanes, or any other of the myriad forms ofnon-conjugated doubly unsaturated hydrocarbons may be used as dilutents.Although they are more reactive, I have also found that any of theisomers or mixed isomers of divinyl benzene may also be used asdiluents, as well as the commercially available low viscosityunsaturated polyesters.

When the liquid polyolefine has functional groups in the molecule, suchas carboxyl, hydroxyl, thiol or amine, an equivalent amount offunctional monomeric reagent is added to allow chain extension to a highmolecular weight. Thus a carboxy containing liquid polymer is chainextended by means of a bifunctional epoxy. Hydroxy compounds and thiolderivatives can be extended by means of diisocyanates of epoxies and thethiols may also be extended by means of epoxies.

In certain of these reactions catalysts are required to initiate chaingrowth. In as much as I can chain extend what I deem internally, bymerely reacting two liquid polyolefines with two different condensableend groups such as NCO and OH, or I can introduce a separate chainextender, externally such as toluene diisocyanates, as an added agent,another external compound as a chain extender would be any of theorganic diepoxides, i.e. available commercially. Since I prefer long potlives at ambient temperatures for the practice of my invention, Inormally limit the amount of initiating catalyst to the minimum levelnecessary to achieve initiation at an elevated temperature. Forcatalysis of chain growth I prefer the reactions to initiate in therange of 70° to 100° C., although lower or higher temperatures may beused. Certain catalysts at low enough concentration and reactivity atambient temperatures may be added at the factory at the time of initialbatch preparation of the castable composition. Otherwise the catalystsare withheld for addition just prior to use. Further catalysis detailsare recited below.

Where the liquid polyolefine is resistant toward polymerization andrequires higher temperatures to achieve initial gelation, I prefer touse a higher melting or less soluble, solid polyolefine powder. I havefound that it is particularly advantageous to have a substantialviscosity increase or gelation occur before reaching the solution ormelting temperature of the solid polyolefine. On the other hand it isalso possible to achieve this initial gelation at somewhat lowertemperatures by the use of a more reactive initiating catalyst. Ineither case the objective is to attain a substantial viscosity increaseor gelation prior to raising the temperature above the solution ormelting temperature of the solid polyolefine to maintain a fixed anduniform distribution of all of the ingredients while the final stages ofpolymerization and grafting are achieved.

In the practice of my invention it will frequently be necessary to havetwo or more different catalysts as well as promotors present to initiatethe different sequential steps of the polymerization. One, for instance,for chain extension and another for reaction with the insulation.Ideally it would be simplest to include all of the catalytic reagents atthe time when all the other ingredients are blended together. In somesystems this will be possible but in most instances it can lead tosubstantially reduced shelf life. Shelf life can be enhanced by the useof common procedures, however. For maximum extension of pot life it isbest to add the catalyst just prior to casting and cure in the splicingmold. Nevertheless, it is within the scope of my invention to add all,one, or none of the catalytic agents at the time of initial mixing ofthe ingredients. This is entirely dependent upon the nature andreactivity of the ingredients and catalysts selected for any givencasting formulation.

As catalysts I have found that the reaction of carboxyl groups withepoxy resins is enhanced by means of chromium salts of oil solubleorganic acids as described in U.S. Pat. Nos. 3,977,996 and 3,978,026.Hydroxy groups will react with isocyanates when catalyzed, for example,by means of organo tin compounds such as dibutyl tin dilaurate or metalchelates, such as ferric acetylacetonate. among others. Amines generallyrequire no other catalysis in reaction with either isocyanates orepoxies and generally the same can be true of thiol compounds atelevated temperatures. However thiols do require free radical initiationfor reactions across a double bond as well as the subsequent graftpolymerization with the solid polyolefin and the cross-linkedinsulation. Therefore, according to my invention, I have found that thecommercially available organic peroxides can be used to catalyze chaingrowth in the reactions of dimercaptans with liquid polyolefines and thegraft polymerization. As catalysts I particularly prefer to use benzoylperoxide, t-butyl perbenzoate, di-t-butyl peroxide, t-butyl-perpivalate,bis-(2-ethylhexyl) percarbonate, dicumyl peroxide, bis-(t-butylperoxy)diisopropylbenzene, 2,5-dimethyl-2 5-di-t-butylperoxyhexane,2,5-dimethyl-2,5-di-t-butylperoxy hexyne-3, n-butyl-4,4-bis(t-butylperoxy) valerate, 1, 1-bis(t-butylperoxy), 3,3,5-trimethylcyclohexane and there are many others. Furthermore it may also beadvantageous to use certain promotors such as cobalt naphthenate ortertiary amines in conjunction with the peroxide catalysts.

As examples of isocyanato compounds that can be employed as chainextending agents herein, for what has been defined as an external chainextension agent, mention may be made of toluene diisocyanate,hexamethylene diisocyanate, diphenymethane-diisocyanate,cyclohexyldiisocyanate, naphtalene diisocyanate, and meta-phenylenediisocyanate, for both --OH and --SH functional liquid polyolefins.

While triisocyanates may be employed, their presence will create or atleast could tend to create excessive crosslinking which gives rise tocontrary physical properties than those desired.

Epoxide pendent groups on the liquid polyolefins can be chain extendedby employing amines, such as: ethylene diamine, phenylene diamines,N-phenylhexamethylenediamine, N,N'-dimethylphenylenediamine. Theseepoxide pendent groups on the liquid polyolefines can also be chainextended by employing dicarboxylic acids, such as: adipic acid, azelaicacid, sebacic acid, and dodecenylsuccinic anhydride,hexahydrophthallylanhydride.

Carboxyl functional groups on the liquid polyolefin can be extended bybifunctional expoxide compounds. Those marketed by the companiesindicated under designs set forth below:

Shell 828; Union Carbide ERL 2795, ERL 2713, EP 201; Dow DER 321, 334,732, 736; diglycidyl ether.

These carboxyl groups can also be extended to form mixtures of hydroxyamides, aminoesters and oxazolines, by reactions with bifunctionalaziridines such as: butyl N, N'diaziridinyl phosphate,bis(1-aziridinyl)benzene, bis(1-aziridinyl)dimethyl ether,bis(2-aziridinyl) dimethyl ether, among others.

All chain extensions to be employed in this invention must chain extendby a condensation reaction and not by the splitting of double bonds.

The following are non-limiting examples:

EXAMPLE 1

The following example illustrates the instant invention in that acombination of hydroxyl and amino polyolefins are reacted withisocyante. This casting composition is then further reacted with thepolyethylene powder and the cable insulation according to thisinvention.

Arco's R45HT (OH substituted Polyolefin): 30 gms

United Technology's ABAN 800 (Amino sub. polyolefin: 10 gms

Toluene diisocyanate: 3.2 gms

Ferric Acetyl acetonate: 0.04 gms

40% DiCup-DAP (defined below): 2 gms.

The above ingredients were thoroughly mixed. A 10 gram sample (a), wasdecanted into a separate container. To the balance, was added 23 gramsof a bimodal blend of polyethylene powder. This mixture was thoroughlystirred and degassed, and then divided into three separate portions.

To portion (b), nothing else was added.

To the vessel containing portion (c) was added a slice of cross-linkedcable insulation, made of polyethylene.

To the vessel containing portion (d) was added a slice of cross-linkedcable insulation made of ethylene-propylene rubber.

All four samples were heated as follows:

30 minutes at 75°-80° C., then

20 minutes at 125°-130° C., then

15 minutes at 150°-160° C.

Cured samples (a) was a tough, resilient rubber. Sample (b) wassubstantially harder than (a) and was a hard, tough though rubberyresin.

The casting compositions when interacted with the cable insulations asin (c) and (d) appeared to adhere well to the insulation as wasdemonstrated by the apparent peel strength in pulling the rubbery resinsfrom the surfaces of the insulation slices.

EXAMPLE 2

To 25 g of R45HT was added 1.9 g of hexamethylene diisocyanate for chainextension. Then 24 g of polystyrene crystals and a mixture of 0.03 gferric acetylacetonate and 1.3 g of 40% DiCup-DAP (40% dicumyl peroxidein diallylphthalate) catalysts was stirred in. The mixture was heated at80° C. for about 30 minutes, gradually raised to 170° C. over 20 minutesand then heated an additional 30 minutes at 170° C. Upon cooling a veryhard, tough resin was obtained. This had reduced unsaturation due tograft polymerization with the polystyrene and would have formed amonolithic structure had cable insulation also been present.

EXAMPLE 3

In the following experiments, I employed a 2800 molecular weight, 2.5hydroxyl groups per molecule hydroxy substituted LPO, namely Arco R45HT.

(a)

LPO: 20 grams

T.D.I.: 1.55 grams

Ferric aceylacetonate (FeAA): 0.03 grams

40% DiCup-DAP: 1 gram

(b)

LPO: 20 grams

Hexamethylene diisocyanate: 1.14 grams

FeAA: 0.02 grams

40% DiCup-DAP: 1 gram

(c)

LPO: 20 grams

Isophorone diisocyanate: 1.86 grams

FeAA: 0.04 grams

40% DiCup-DAP: 1 gram

Ten gram portions of each of 3a,3b and 3c were dispersed with 8 grams ofa bimodal mix of polyethylene and polypropylene powders, and poured intoa mold surrounding a section of cured polyethylene cable insulation.Each container (mold) was heated at 75° to 80° for 30 minutes, duringwhich time gellation took place. The temperature was raised to 125°-130°for 20 minutes and finally to 150°-160° for 15 minutes. It was found oncooling that a tough uniform composite structure had been formed withthe insulation that was difficult to peel off.

As is known, a bimodal or polymodal blend constitutes a mixture in astated ratio of small size to large size particles such that oncomposition the small particles fill the spaces between the large onesto enhance the density of the material.

MOLD MANUFACTURE AND USE--EX. 4

The following constitutes a procedure for the preparation of a mold tobe utilized in accordance with the techniques of this invention for thepreparation of splices of high-voltage cable. It is readily understoodthat when molds 80, necessary to this invention, are to be prepared on acommercial basis other modes of manufacture that are more conducive tolower costs may be employed.

An aluminum mold 80 was prepared by cutting a 14" length of 2" wideschedule 5 aluminum tubing. According to specification, this materialhas a 2.375 inch outside diameter and a 2.25 inch inside diameter. Toeach end was brazed a 60° cone of aluminum with the larger diameter ofthe cone equal to the exterior diameter of the tube. A portion of thetapered section of each cone was removed to leave a 15/16" opening ateach end, 104. The tube with 2 tapering ends was then longitudinallysawed in half. To one of the halves at 4" from each end, in a straightline, was brazed a 1" length of 3/8" O.D. aluminum tubing which had beenpreviously flared to provide a funnel-like opening. Holes were drilledthrough the inside diameters of the funnel tubes to provide fluidcommunication of the funnel to the main part, or chamber of the mold.The configuration of the two halves was to ensure that the longitude ofthe mold halves correctly abutted along the entire length thereof toprevent leakage of cast mix when such is added through the funnel tubes.This construction differs slightly from that of the figures, but the neteffect of having funnel openings is the same.

The interior of each half of the mold was thoroughly cleaned and severalcoats of semi-conducting paint were applied with adequate time beingprovided for drying between the applicator of each coat. A total layerof thickness of about 1/16" was found suitable. The mold was now readyfor use.

Two 12" lengths of 27 KV aluminum power cable having an O.D. of 15/16"were cut and trimmed as shown in FIG. 2, leaving 2" bare conductorexposed followed by 3/4" of semi-conductor cable screen. A metal crimpwas used to join the conductors. After sanding and wiping with acetone,two layers of semi-conducting tape were wrapped over the bare wire andthe crimp seal overlapping the semi-conductor shield of the cable. Thealuminum shell mold was placed symmetrically around the spliced cableand clamped tightly over the cable by means of standard screw tightenedclamps. The assembly was placed in a horizontal position with the funneltubes upstanding and ready for cast addition.

A 1000 gram batch of the formulation of Example 3a which had beenpreviously prepared was added through one of the inlet funnels andallowed to flow into and fill the mold chamber up into the two inlettubes approximately half way to the top of the funnels. The assembly wassupported in a horizontal position, placed in an oven at 75°-80° C. for90 minutes for gelation to transpire. The temperature was raised to125°-130° C. for an hour, and finally to 150°-160° C. for another 80minutes. Upon cooling, a monolithic electrical splice assembly wasrecovered. The insulation material, which was cross linked polyethylenewas found to be fully bonded to the material which had been cast intothe mold and allowed to harden.

When dielectric strength measurements are run of castings made fromcompositions employable in this invention, by ASTM test D149, it isfound that measurements in the range of 500-600 volts per mil. areobtained.

Since certain changes may be made in the above products, compositionsand processes without departing from the scope of the invention hereininvolved, it is intended that all matter contained in the abovedescription shall be interpreted solely as illustrative and not in alimiting sense.

What is claimed is:
 1. Spliced high voltage cable prepared from asplicing of two insulation and conductor portions, said spliced cablecomprising:electrically and mechanically joined conductor portions, anda monolithic cured polymeric insulation splice prepared by the reactionof a castable mixture comprising a liquid polyolefin having pendentgroups capable of entering into a condensation reaction, a chainextension agent reactive with said pendent groups, and a particulatedsolid saturated polyolefin with the two insulation portions.
 2. Thecable splice of claim 1 wherein the castable mixture contains an organicdiluent.
 3. The cable splice of claim 1 wherein the castable mixturecontains a catalyst.
 4. The cable splice of claim 1 wherein the liquidpolyolefin's pendent groups are selected from the group consisting ofhydroxy, carboxy, amino, thio, epoxy and isocyanato.
 5. The cable spliceof claim 1 wherein the insulation portions are selected from the groupconsisting of crosslinked polyethylene, and crosslinkedpolyethylene-propylene.
 6. The cable splice of claim 1 wherein theparticulated solid polyolefin is selected from the group consisting ofsaturated polyethylene, polypropylene, and polystyrene.
 7. Spliced highvoltage cable prepared from a splicing of two insulation and conductorportions said cable slice comprising:electrically and mechanicallyjoined conductor portions, and a monolithic cured polymeric insulationsplice prepared by the reaction of a castable mixture comprising aliquid polyolefin having pendent groups selected from the groupconsisting of hydroxyl and isocyanato, a chain extension agentcomprising an organic compound having hydroxyl functionality when saidpendent groups are isocyanato, and having isocyanato functionality whensaid pendent groups are hydroxyl, and a particulated saturatedpolyolefin with the cable insulation.
 8. Spliced cable as in claim 7wherein the insulation is selected from the group consisting ofcrosslinked polyethylene or polypropylene, and the reaction with thecastable mixture is carried out as a two step two temperature reaction.9. Spliced high voltage cable as in claim 1 wherein the reaction of thecastable mixture with the insulation is carried out as a two step twotemperature reaction.
 10. Spliced cable as in claim 8 wherein thecastable mixture further includes an organic diluent and a catalyst. 11.Spliced high voltage cable prepared as in claim 1 wherein the liquidpolyolefin is a compound of the formula: ##STR4## wherein Vi is a vinylside chain; Bi is the backbone of the polymer and contains at least oneunsaturated double bond; G represents non-reactive side groupsubstituents selected from the group consisting of cycloalkyl, alkyl,aryl, aralkyl, iodo, bromo, chloro, cyano, carbalkoxy, and alkoxy; Fn isa functional chain-extendable moiety selected from the group consistingof: --OH, --COOH, --NH₂, --SH, --C═CH, --NCO, and ##STR5## each of whichmay be the same or different; wherein m is a number of at least one, xis a number from 0 to about 5; Fn is a moiety and q designates amolecular weight range of 300 to 10,000.